If any emergency situation should occur, and if the head and/or neck are not protected by the headrest, or if the upper body is not protected by the seat back (upper frame/seat back frame), whiplash or other injuries may occur. Thus, various countermeasures have been taken. However, it became apparent that in the event of an emergency situation, the strength of the headrest (including the bracket or upper frame) and side frame is not sufficient. One example of such insufficient strength is seen in FIG. 27 which shows the upper frame deflected by the force of a collision (Deflection X), thus disclosing the lack of strength.
Therefore, it is necessary to obtain an appropriate structure of the bracket and upper frame, or of each structure or series of structures of the upper frame/side frame, so that problems such as lack of strength are solved. The countermeasures to be taken in the conventional arts will be reviewed here. The countermeasures should be taken comprehensively and variedly without limiting the structure of the bracket and upper frame, of each structure or series of structures of the upper frame/side frame.
The first subject, “Structure of Bracket and Upper Frame” refers to Japanese Published Unexamined Application No. 2005-138754, entitled “Supporting Structure of Headrest for Vehicles” and No. H08-182569, entitled “Structure of Seatback Frame.” Either structure has a common feature in which the bracket is welded onto a flat attaching portion which is provided by pressing the upper frame. Thus, the welding is vertically done. That is, the welding is done on the surface (in the direction of vehicle movement). Therefore, as shown in FIG. 27, the upper frame is deflected upon collision impact, thus showing its inherent weakness.
The second subject, “Auxiliary Means for Improving the Strength of the Structure of the Bracket and Upper Frame” refers to Japanese Published Unexamined Application No. 2008-207807, entitled “Supporting Structure of Headrest” and No. 2002-315649, entitled “Seatback Frame for Vehicles.” The former application discloses that the strength of the upper frame is improved by providing the upper frame with a reinforcing plate. The latter application discloses a structure of a pair of protrusions opposingly formed within the attaching portion of the upper frame and bracket, with those protrusions being welded together.
The third subject, “Structure of Side Frame (front and rear panels)” refers to Japanese Published Unexamined Application No. 2004-322881, entitled “Seatback for Vehicles” and No. 2002-283893, entitled “Seatback Frame of Seat for Vehicles” and No. H07-31526, entitled “Seatback Frame.” The side frame unit comprising side panels in which the front and rear panels have a special structure, or in which another structure such as an insert brace, a reinforcing bead or the like is added.    Patent Document 1: Japanese Published Unexamined Application No. 2005-138754    Patent Document 2: Japanese Published Unexamined Application No. H08-182569    Patent Document 3: Japanese Published Unexamined Application No. 2008-207807    Patent Document 4: Japanese Published Unexamined Application No. 2002-315649    Patent Document 5: Japanese Published Unexamined Application No. 2004-322881    Patent Document 6: Japanese Published Unexamined Application No. 2002-283893    Patent Document 7: Japanese Published Unexamined Application No. H07-31526